In the middle of enjoying a spectacularly colored sunrise or sunset like the one in the photo above, have you ever stopped to ask why it is that the sky turns such colors when the sun is low in the sky? It is all about the distance that light has to travel to get to our eyes, which is much farther when the sun is at the horizon than when it is directly overhead.
Portage Inc explains it well:
During sunrise and sunset, when the sun lies low on the horizon, the rays of sunlight must pass through almost 30 percent more area of atmosphere than they do during the day, and a higher number of larger atmospheric particles (i.e., dust, or water vapor) before they reach us. The shorter violet and blue wavelengths scatter away from our field of vision. However, the longer wavelengths of light do not scatter as much and the sky becomes filled with yellow, orange and red. Red has the longest wavelength in the visible spectrum, so when the sun lies on the horizon, it appears red. During a rainstorm, the water vapor in the air acts like a prism, separating light by the various wavelengths. This is why we see rainbows. The angle is important to seeing the separate colors, which is why when we move the rainbow appears to move.
Stephen Corfidi, a National Oceanic and Atmospheric Administration (NOAA) meteorologist, makes an excellent point in a Q&A with National Geographic about the intensity of light and what makes a sunset or sunrise particularly “good”:
Everything is connected. And as humans, we like to think color is concrete: ‘Oh, that’s a blue sky,’ or ‘That’s a brown table.’ But the colors you see depend on the light’s path before it got to you, how the object you are viewing reflects that light, and what your eyes are sensitive to. Absolutes don’t really exist in color perception. It’s rather disquieting when really you start thinking about it!
So, essentially, everyone experiences a sunset in their own unique way, depending on countless tiny factors. The science as well as the individual experience is something that can be discussed for hours on end.